Passenger car and commercial vehicle manufactures are turning to hybrid vehicles as a way to meet increasingly stringent emissions standards such as the Corporate Average Fuel Economy (CAFE) requirements. Hybrid vehicles use two or more power sources to achieve vehicle propulsion. Although most often associated with an electric motor in combination with an internal combustion engine, hybrid vehicles are not limited to these particular power sources. In addition to reduced emissions, hybrid vehicles offer improved fuel economy relative to conventional non-hybrid vehicles.
However, despite the clear benefits of using hybrid vehicles, they are costly to manufacture and vehicle driving ranges remain limited by current battery technologies. For these reasons, an improved vehicle drive system is needed that can address these issues.